MEMS tunable silicon fabry-perot cavity and applications thereof

• US 20090153844A1
• Filed: 08/11/2008
• Published: 06/18/2009
• Est. Priority Date: 08/10/2007
• Status: Active Grant

• Current Assignee: Polyvalor LP
• Original Assignee: Polyvalor LP
• Inventors: Peter, Yves-Alain, Masson, Jonathan, St-Gelais, Raphael
• Granted Patent: US 8,174,698 B2
• Time in Patent Office: Days
• US Class Current: 356/128
• CPC Class Codes: G01N 2021/0346 Capillary cells; Microcells
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/41 Refractivity; Phase-affecting properties, e.g. optical path length G01N21/21 takes precedence
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/29376 coupling light guides for controlling wavelength dispersion, e.g. by concatenation of two light guides having different dispersion properties dispersion managed optical transmission systems H04B10/25253
• CPC Class Codes: G02B 6/29394 Compensating wavelength dispersion G02B6/29376 takes precedence; dispersion compensated optical transmission systems H04B10/2507
• CPC Class Codes: H01S 3/0675 Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
• CPC Class Codes: H01S 3/06791 Fibre ring lasers fibre laser gyrometers G01C19/72
• CPC Class Codes: H01S 3/08027 by a filter, e.g. a Fabry-Perot filter is used for wavelength setting
• CPC Class Codes: H01S 3/1062 using a controlled passive interferometer, e.g. a Fabry-Perot etalon

Abstract

A method for fabricating a tunable Fabry-Perot cavity comprises etching a substrate to form two reflectors separated by an air gap and an electrostatic mechanism. One of the two reflectors is mobile and connected to the electrostatic mechanism. Therefore, operation of the electrostatic mechanism moves the mobile reflector to change the thickness of the air gap and thereby tune the Fabry-Perot cavity. A tunable Fabry-Perot cavity fabricated with the above method comprises: a substrate; two reflectors formed in the substrate and separated by an air gap having a thickness, wherein one of the two reflectors is mobile; and an electrostatic mechanism formed in the substrate and connected to the mobile reflector. The mobile reflector connected to the electrostatic mechanism is moved upon operation of the electrostatic mechanism to change the thickness of the air gap and thereby tune the Fabry-Perot cavity. Applications of the Fabry-Perot cavity may comprise a tunable doped fiber laser, a tunable dispersion compensator and an integrated microfluidic refractometer.

Claims

1. A method for fabricating a tunable Fabry-Perot cavity, the method comprising

etching a substrate, wherein etching the substrate comprises:

forming two reflectors separated by an air gap having a thickness, wherein one of the two reflectors is mobile on the substrate; and

forming an electrostatic mechanism connected to the mobile reflector;

wherein the mobile reflector connected to the electrostatic mechanism is moveable under the operation of the electrostatic mechanism so as to change the thickness of the air gap and thereby tune the Fabry-Perot cavity.

2. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 1, wherein etching the substrate comprises forming fiber integration grooves for aligning input and output optical fibers.

3. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 1, wherein forming the electrostatic mechanism comprises forming a comb drive actuator.

4. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 1, further comprising providing a multi-layer substrate forming the etched substrate.

5. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 4, wherein providing the multi-layer substrate comprises providing a substrate with a first layer of silicon, a second layer of oxide of silicon and a third layer of silicon.

6. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 4, further comprising applying a photoresist layer to the multi-layer substrate.

7. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 6, further comprising performing a photolithography of the photoresist layer applied to the multi-layer substrate.

8. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 4, wherein etching the substrate comprising vertically etching the multi-layer substrate.

9. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 8, wherein vertically etching the multi-layer substrate comprises using Inductively Coupled Plasma (ICP) deep reactive ion etching (DRIE).

10. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 5, wherein etching the multi-layer substrate comprises etching away the layer of silicon oxide so as to release the tunable Fabry-Perot cavity.

11. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 10, further comprising performing CO2 drying of the Fabry-Perot cavity to prevent the Fabry-Perot cavity from sticking.

12. A method for fabricating a tunable Fabry-Perot cavity as defined in claim 2, further comprising passively aligning input and output optical fibers in the fiber integration grooves.

13. A method for tuning a Fabry-Perot cavity having two reflectors formed into a substrate and separated by an air gap having a thickness, wherein one of the two reflectors is mobile and wherein the method comprises:

forming an electrostatic mechanism in the substrate;

connecting the electrostatic mechanism to the mobile reflector; and

operating the electrostatic mechanism to move the mobile reflector connected thereto;

wherein moving the mobile reflector connected to the electrostatic mechanism changes the thickness of the air gap and thereby tune the Fabry-Perot cavity.

14. A method for tuning a Fabry-Perot cavity as defined in claim 13, wherein forming the electrostatic mechanism comprises forming a comb drive actuator in the substrate.

15. A method for tuning a Fabry-Perot cavity as defined in claim 14, wherein connecting the electrostatic mechanism to the mobile reflector comprises connecting the comb drive actuator to the mobile reflector.

16. A method for tuning a Fabry-Perot cavity as defined in claim 14, wherein operating the electrostatic mechanism comprises applying a voltage to the comb drive actuator.

17. A method for tuning a Fabry-Perot cavity as defined in claim 13, wherein operating the electrostatic mechanism comprising achieving a uniform modulation of the thickness of the air gap.

18. A method for tuning a Fabry-Perot cavity as defined in claim 13, further comprising reducing the thickness of the air gap, wherein reducing the thickness of the air gap comprises reducing a filtered wavelength of light propagating through the Fabry-Perot cavity.

19. A tunable Fabry-Perot cavity comprising:

a substrate;

two reflectors formed in the substrate and separated by an air gap having a thickness, wherein one of the two reflectors is mobile; and

an electrostatic mechanism formed in the substrate and connected to the mobile reflector;

wherein the mobile reflector connected to the electrostatic mechanism is moved upon operation of the electrostatic mechanism to change the thickness of the air gap and thereby tune the Fabry-Perot cavity.

20. A tunable Fabry-Perot cavity as defined in claim 19, wherein the substrate is a multi-layer substrate.

21. A tunable Fabry-Perot cavity as defined in claim 20, wherein the multi-layer substrate comprises a first layer of silicon, a second layer of oxide of silicon and a third layer of silicon.

22. A tunable Fabry-Perot cavity as defined in claim 19, wherein the two reflectors each comprise three walls.

23. A tunable Fabry-Perot cavity as defined in claim 19, further comprising fiber alignment grooves formed in the substrate for passively aligning input and output optical fibers.

24. A tunable Fabry-Perot cavity as defined in claim 19, wherein the two reflectors comprise the mobile reflector and a fixed reflector.

25. A tunable Fabry-Perot cavity as defined in claim 19, wherein the electrostatic mechanism comprises a comb drive actuator.

26. A tunable Fabry-Perot cavity as defined in claim 25, wherein the comb drive actuator is connected to the mobile reflector.

28. A tunable Fabry-Perot cavity as defined in claim 19, wherein the two reflectors and the electrostatic mechanism are fabricated in the substrate through a single etching process.

29. A tunable doped fiber laser, for generating laser at different wavelengths, comprising:

a laser source;

a doped fiber connected to the laser source; and

a tunable Fabry-Perot cavity including (a) a substrate;

(b) two reflectors formed in the substrate and separated by an air gap having a thickness, wherein one of the two reflectors is mobile; and

(c) an electrostatic mechanism formed in the substrate and connected to the mobile reflector, wherein the mobile reflector connected to an electrostatic mechanism is moved upon operation of the electrostatic mechanism to change the thickness of the air gap and thereby tune the Fabry-Perot cavity, the tunable Fabry-Perot cavity being connected to the doped fiber;

wherein tuning the tunable Fabry-Perot cavity allows for selecting different laser wavelengths.

30. A tunable doped fiber laser as defined in claim 29, wherein the doped fiber comprises an Erbium-doped fiber.

31. A tunable doped fiber laser as defined in claim 29, wherein the laser source comprises a laser diode.

32. A tunable doped fiber laser as defined in claim 31, further comprising a wavelength division multiplexer (WDM) coupler connected to the laser diode.

33. A tunable doped fiber laser as defined in claim 32, further comprising an isolator connected to the WDM coupler for controlling a direction of a laser signal.

34. A tunable doped fiber laser as defined in claim 29, further comprising a tap used as an output coupler and connected to the tunable Fabry-Perot cavity.

35. A tunable dispersion compensator for adjusting a group delay experienced by light when propagating through an optical fiber, the tunable dispersion compensator comprising:

a tunable Gires-Tournois cavity comprising two reflectors separated by an air gap, wherein one of the two reflectors is mobile and a mechanism is connected to the mobile reflector to move the mobile reflector; and

a waveguide positioned between the two reflectors;

wherein moving the mobile reflector modulates a reflectivity of the tunable Gires-Tournois cavity and thereby adjust the group delay.

27. A tunable Fabry-Perot cavity as defined in claim 35, wherein the comb drive actuator comprises a comb drive suspended from the substrate by a set of springs.

36. A tunable dispersion compensator as defined in claim 35, further comprising a single mode input fiber connected to the tunable Gires-Tournois cavity.

37. A tunable dispersion compensator as defined in claim 36, further comprising a gradient-index (GRIN) fiber, merged with the single mode input fiber for providing an increased diameter of an incident light beam.

38. A tunable dispersion compensator as defined in claim 35, wherein the compensator comprises two tunable dispersion compensators positioned in series.

39. A tunable dispersion compensator as defined in claim 38, further comprising a circulator connected to each of the two tunable dispersion compensators positioned in series for controlling a light propagation direction.

40. A tunable dispersion compensator as defined in claim 35, wherein the compensator is fabricated in a substrate through photolithography and etching processes.

41. An integrated microfluidic refractometer for measuring a refractive index of a fluid including at least one of a liquid and a gas, the refractometer comprising:

a Fabry-Perot cavity; and

a microfluidic channel, connected to the Fabry-Perot cavity, for carrying the fluid to the Fabry-Perot cavity;

wherein the Fabry-Perot cavity detects a shift of wavelength corresponding to a variation of the refractive index when the fluid passes through the Fabry-Perot cavity.

42. An integrated microfluidic refractometer as defined in claim 41, further comprising a reservoir for containing the fluid to be measured.

43. An integrated microfluidic refractometer as defined in claim 41, wherein the Fabry-Perot cavity comprises two reflectors each comprising three layers of silicon and two layers of air.

44. An integrated microfluidic refractometer as defined in claim 41, wherein the microfluidic channel uses a capillary effect to carry the fluid to the tunable Fabry-Perot cavity.

45. An integrated microfluidic refractometer as defined in claim 41, wherein the refractometer is fabricated through a single photolithography and etching process.

46. An integrated microfluidic refractometer as defined in claim 45, wherein the etching process comprises an optimized bosch process.

47. An optical attenuator for attenuating light transmission, comprising:

a substrate;

two reflectors formed in the substrate and separated by an air gap, wherein one of the two reflectors comprises an inner wall, a central wall and an outer wall separated from each other by other air gaps having respective thicknesses, and wherein the central wall is mobile; and

an electrostatic mechanism formed in the substrate and connected to the mobile wall;

wherein the mobile wall connected to the electrostatic mechanism is moved upon operation of the electrostatic mechanism to change the thicknesses of said other air gaps and thereby change reflectivity in the optical attenuator and attenuate light transmission through the optical the attenuator.